TODO

TODO (not in this order):

• support more listing platforms
• replace GeoJSON stuff by direct GPX-reading layer
• rewrite in a more structured manner (now that I know what I’m doing);
  this is a rapid prototype to prove doability and that it works in Opera 9
• merge CGIs, possibly using AJAX (if it works in Opera 9) to make them
  into layers
• make CGIs dynamic wrt. current map boundaries (if zoom > minzoom)
• maybe CGI-using GPX import, for Opera/Konqueror who can’t do it client-side
• create user docs

Note also that this is a rapid-prototype PoC…

https://github.com/tmcw/togeojson is more maintained than
the toGeoJSON stuff we currently have in the repo. Though
it might not work on all browsers (any more)… see above.

https://wiki.openstreetmap.org/wiki/Tiles
• MapTiler
• MapTiles (rapidapi)
• waymarkedtrails

https://learn.microsoft.com/en-us/azure/azure-maps/zoom-levels-and-tile-grid?tabs=typescript
• uses 85.05112878 as clipping latitude inexactly; exact is:
  ‣ sin¯¹( (e(2*π)-1) / (e(2*π)+1) ) * 180/π
  ‣ a(((e(2*p)-1)/(e(2*p)+1))/sqrt(1-((e(2*p)-1)/(e(2*p)+1))*((e(2*p)-1)/(e(2*p)+1))))*180/p
  ≈ 85.05112877980659237779671552192469206698259126842068840576245939159
  ← leaflet uses 85.0511287798 which is… only marginally better
• better clip check:
    var sinLatitude = Math.sin(latitude * Math.PI / 180);
    var y = 0.5 - Math.log((1 + sinLatitude) / (1 - sinLatitude)) / (4 * Math.PI);
  → make sure 0≤y<1 (≤1 will do, given the follow-up clipping)
    (though latitude still must be in ]-90;90[ or this will div by zero!)
• explains map zoom levels (L.TileLayer and TMS)
  and pixel coordinates, graphically and with sample code
• quadkey indicēs (great!)